Biotyping of coagulase-negative staphylococci. 108 isolates from nosocomial bloodstream infections.
Using simple, readily available typing methods, we evaluated 108 strains of coagulase-negative staphylococci that were causally related to bloodstream infections: 95% (103 of 108) of the isolates were identified as Staphylococcus epidermidis and were divided into 18 biotypes by API Staph-Trac. A single biotype (biotype A, 6606113) accounted for greater than 50% of the isolates of S. epidermidis. Biotype A was further divided into seven subtypes by slime production and synergistic hemolysis; however, 66% of the isolates in biotype A remained in two major subtypes, 1a (strongly slime-positive and synergistic hemolysis-positive) and 2a (strongly slime-positive and synergistic hemolysis-negative). The addition of the antibiotype further separated the isolates into individual strains or into small groups of organisms. A significant correlation was noted between synergistic hemolysis and the three most resistant antibiotypes (p = 4.2 X 10(-5); OR = 5.8; CI95, 2.2-15.2). Each biotype, subtype, and antibiotype was further divided into multiple unique strains by plasmid pattern analysis. In most clinical situations the combination of API Staph-Trac, antibiotic profile, slime production, and synergistic hemolysis provides adequate strain discrimination. Plasmid pattern analysis adds important information in specific clinical situations and may be invaluable for epidemiologic investigations.
Herwaldt
L A
LA
Department of Internal Medicine, University of Iowa College of Medicine, Iowa City 52242.
Boyken
L D
LD
Pfaller
M A
MA
D015373:Bacterial Typing Techniques; D003030:Coagulase; D003428:Cross Infection / Q000382:microbiology*; D004269:DNA, Bacterial / Q000032:analysis; D006801:Humans; D010957:Plasmids; D011446:Prospective Studies; D015203:Reproducibility of Results; D012189:Retrospective Studies; D018805:Sepsis / Q000382:microbiology*; D013203:Staphylococcal Infections / Q000382:microbiology*; D013210:Staphylococcus / Q000145:classification* / Q000201:enzymology / Q000235:genetics
D003030:Coagulase; D004269:DNA, Bacterial